Process of bleaching soap



Patented Jan. 13, 1931 UNITED STATES PATENTV OFFICE CHARLES FRANKSCHUMAKER, OF SYRACUSE,

NEW YORK, ASSIGNOR TO THE MATHIE' SON ALKALI WORKS, INC-, OF NEW YORK,N. Y., A CORPORATION OF VIRGINIA PROCESS OF BLEAGHTNQ SOAP No Drawing.

This invention relates to the bleaching of soap to produce a stablebleached soap product.

It has heretofore been proposed to bleach soa by the action ofhypochlorites but in sue processes chemical action other than bleachinga parently takes place and interferes with t e bleachin process. Wherethe soap has been bleache y the hypochlorite the bleached product hasapparently been unstable and lacking in permanent whiteness. So far as Iam aware the bleaching of soap with hypochlorite according to processesheretofore proposed has not been successfully carried out in acommercial manner.

The present invention provides an improved process for bleaching soap inwhich the bleaching is effectively carried out and a stabilized productproduced which can be kept for long periods of time in a bleached I orwhite condition. I

I have found that soap can be readily and satisfactorily bleached by thecombined action of sodium hypochlorite and formaldehyde,-whichapparently gives a permanently bleached roduct. Sodium hypochlorite andformaldehyde in solution react with each other forming, among theirreaction products formic acid, h pochlorus acid and sodium formate. Theringing together of solutions of sodium hypochlorite and formaldehyde inintimate admixture with soap exerts a rapid bleaching action on thesoap. This bleaching action appears to be due in part to the action ofhypochlorous acid formed from the reaction of sodium h pochlorite andformaldehyde. It is proba le that the formaldehyde is first in partoxidized to formic acid which reacts with sodium hypochlorite to formsodium formate and hypochlorous acid. Sodium formate is the sodium saltof the simplest of the fatt acids and is itself a desirable ingredient othe soap. Hypochlorous acid is an active bleaching agent. It isprobable. that the sodium hypochlorite and the formaldehyde have otheractions on the soap which contribute to the bleaching operation and tothe production of a stable and preserved product. It is probable thatthe sodium hypochlorite acts in part to oxidize Application filed June26,

1928. Serial No. 288,144.

acts with additional sodium hy ochlorite to set free hypochlorous acidand orm sodium formate, but it may be that the formaldehyde mayotherwise react with the sodium hypochlorite or with the hyp'ochlorousacid. Formaldehyde is a valuable preservative agent, having importantreducing properties because of its aldehydic character and the use ofsuch a preservative agent appears to be important in producing ableached soap of a stable bleached character, which resists the tendencyto change from its white bleached state to a discolored state such ascharacterizes various soap products heretofore bleached with sodiumhypochlorite.

I consider accordingly that my process in which sodium hypoc loriteandformaldehyde are employed is one in which the fatty acid, i. e.,formic acid, is formed from the aldehyde, i. e., formaldehyde, and inwhich the fatty acid reacts with the sodium hypo chlorite to formhypochlorous acid as an ac- 3 tive bleaching agent, and also one inwhich the aldehyde has important properties as a stabilizing agent .orinhibitor of subsequent oxidation or deterioration. Whereas productsbleached with'sodium hypochlorite alone reagent 1s added so that thereaction takes place with the reagents intimately distributed throughoutthe soap.

The amounts of hypochlorite and formaldehyde can be somewhat varied, butusually not more than about 2% of sodium hypochlorite and 1% offormaldehyde are required. The formaldehyde can conveniently commercialwater be used in the-form of the mg and the degree solution containingaround 37-40% of formaldehyde. The sodium hypochlorite canadvantageously be added dissolved in water.

In the manufacture of soaps, the soap, after the boiling operation, issettled and separated from the lye and the still liquid soap. issubjected to a crutching operation where various materials, such asfillers, perfume, etc. are added and the soap thoroughly mixed. The soapfrom the crutcher is commonly run into frames where it is permitted tosolidify, after which it is cut into slabs and bars and dried. Thehigher rades of soap, such as toilet soaps, are made y shaving the soapto form chips, which are then milled and formed into the final cakes. Inother. methods of making toilet soaps the crutching operation is omittedand the soap on completion of the boiling operation is run to acontinuous drying chamber where it is dried, after which it is chippedand subjected to a milling operation. In such case the chips may beamalgamated with perfume and other ingredients milling. p 7

'The bleaching process of the present invention can advantageously becarried out during or as a part of the milling operation, but it canalso be carried out in part or in whole'during an earlier part of thesoap making operation, and particularly during the crutchingoramalgamating operation.

When the bleaching operation is carried out in connectionwith themilling of the soap, the soap chipsshould contain a suit able content ofmoisture, usually around 8 to 14%, depending upon the type of mill used.The effectiveness of the bleaching operation, however, does not appearto be debefore subjecting to pendent upon the moisture content of thechips.

The invention will be further illustrated by the following specificexamples, but it will be understood that the invention is not limitedthereto. Soap chips having a moisture content of around 8 to 14% aremixed with the solution of sodium hypochlorite and the solu tion offormaldehyde, the precentage depending upon the color of the soap beforebleachof bleaching action desired. Usually not more than 2% ofhypochlorite and 1% of formaldehyde are required. After the chips havebeen thoroughly mixed with the hypochlorite and formaldehyde they arepassed through a soap mill one or more times. The greater part ofthebleaching action takes place during the'milling process, due in'allprobability to the activity of the bleaching agents under mechanicalpressure and the slight heat of the mill and the intimate contactbrought about by the milling operation. An arrangement of, two mills intandem appears to make the best pochlorite dissolve can be runarrangement for carrying out the process I when the bleachingingredients are added in a single operation.

Instead of adding the bleaching ingredients in a single operation,either the sodium hypochlorite solution or the formaldehyde solution maybe added in the initial milling and the other added for the secondmilling. For example, the sodium hypochlorite solution. may be addedfirst and the soap. milled after which the formaldehyde is added and thesoap again milled; or this process can be reversed and the formaldehydesolution added before the first milling and the sodium hypochloritesolution before the second milling.

According to another example of the invention a definite ercentage ofsodium hyd in water is added to the liquid soap'properly finished as itcomes from the soa kettle so that the sodium hypochlorite so ution isincorporated into the plastic mass of the soap during the crutchingoperation.

Subsequently the soap is dried and chipped and the soap chips with thecustomary moisture content for milling are mixed with a definitepercentage of formaldehyde dissolved in water and subjected to themilling operation. g

When formaldehyde solution is added to soap already intimately admixedwith sodium hypochlorite, or vice versa, or-where both the hypochloriteand formaldehyde solutions are added during the same operation, adecided bleaching action takes place,'which is markedly different fromthat obtained when sodium hypochlorite alone is added to soap. Thisbleaching action accordingly appears to be-due largely to reactionproducts produced by the interaction of the hypochlorite andformaldehyde upon each other in intimate admixture with soap, such ashypo chlorous acid and nascent oxygen.

excess of formaldehyde, in excess of its complete oxidizing and.bleaching action during the bleaching operation without leaving anyresidual oxidizing agent present and instead leaving more or lessformaldehyde which has reducing properties and acts as a preservative'orinhibitor of oxidation.

In the carrying out of the present process the hypochlorite andformaldehyde solutions can bestored in suitable containers suspendedabove the mixer or mixers or otherwise arranged so that definitequantities of each into the soap chips either as a bleach the soap.

batch operation or as a continuous operation. By arranging the mixer andmills so that the operations follow each other continuously and byadding the bleaching reagents in a continuous and regulated manner, thebleaching operation as a whole can be made continuous.

An excess of one of the bleaching reagents, particularly formaldehyde,is desirable in the nal product in order to impart improved stabilityand I claim 2- 1. The process of bleaching soap which comprisessubjecting the soap to a milling operation in intimate admixture withsolutions of sodium hypochlorite and formaldehyde.

2. The process according to claim 1 in which the sodium hypochlorite andformaldehyde dissolved in water are added to the soap chips beforemillingand caused to act upon the soap during the subsequent millingoperation.

3. The process of bleaching soap with sodium hypochlorite andformaldehyde which comprises mixing the soap before milling with one ofsaid agents and subjecting the soap to milling, then mixing theresulting soap with the other reagent and subjecting the soap to asecond milling operation.

4. The process of bleaching soap which comprises adding to the soapsodium hypochlorite dissolved in water and subjecting the soap to acrutching operation, drying and chipping the resulting soap, mixing withthe soap chips a solution of formaldehyde and milling the resultingmixture.

5. The method according to claim 1 in which an excess amount of sodiumhypochlorite is used over the amount required to anitseptic or otherproperties.

6. The process of bleaching soap which comprises subjecting the soap tothe action of free hypochlorous acid, the hypochlorous acid beinggenerated in a nascent state during the bleaching operation by theaction on an alkaline hypochlorite of an acid.

7. The process of bleaching soap which comprises subjecting the soap tothe action o f free hypochlorous acid, the hypochlorous acid beinggenerated in a nascent state during the bleaching operation by theaction on an alkaline hypochlorite of formic acid produced fromformaldehyde during the bleaching operation.

8. The process of bleaching soap which comprises subjecting the soap tothe action of an alkaline hypochlorite and formaldehyde.

9. The method of-bleaching soap which comprises subjecting the soap tothe action of hypochlorous acid and formaldehyde which stabilizes thebleached soap against afterdarkening.

10. The process of bleaching soap which comprises subjecting the soap toa mechanical workin operation with addition thereto of an alka inehypochlorite and formaldehyde, the aldehyde being in excess so as toleave some of the formaldehyde in the bleached product.

11. The method of bleaching soap which comprises incor orating with thesoa an alkaline hypoc lorite and formalde yde which will react with thehy chlorite to form free hypochlorous acid, t e formaldehyde beingemployed in sufiicient excess to stabilize the resulting bleachedproduct against after-darkening.

' whereof I afiix my signature.

In testimony CHARLES FRANK SCHUMAKER.

